* {
    margin: 0;
}
body {
    padding-bottom: 50px;
}
.controls {
    margin: 10px 20px;
}
.content {
    position: relative;
    height: 300px;
    border: 2px dashed #e1251b;
}
.core {
    position: absolute;
    left: 0;
    top: 0;
    width: 150px;
    height: 150px;
    background-color: darkorange;
}
.content1 {
    height: 150px;
}
/* #core2:hover {
    background-color: aqua;
    transition: background-color 1s ease;
} */